Deltoid Muscle: Anatomy and Function
Overview
The deltoid muscle is a large, triangular muscle that covers the shoulder. It is the primary muscle responsible for abducting (lifting away from the body), flexing (bending forward), and rotating the arm.
Anatomy
The deltoid muscle has three heads:
- Anterior (front) head: Originates from the clavicle (collarbone) and inserts into the anterior (front) surface of the humerus (upper arm bone).
- Lateral (side) head: Originates from the acromion process (bony projection on the top of the shoulder blade) and inserts into the lateral (side) surface of the humerus.
- Posterior (back) head: Originates from the spine of the scapula (shoulder blade) and inserts into the posterior (back) surface of the humerus.
The deltoid muscle is innervated by the axillary nerve.
Function
The deltoid muscle has the following functions:
- Abduction: Lifts the arm away from the body.
- Flexion: Bends the arm forward.
- Rotation: Rotates the arm inward (medial rotation) and outward (lateral rotation).
Clinical Significance
Injuries to the deltoid muscle can occur due to overuse, trauma, or nerve damage. Common injuries include:
- Deltoid strain: A tear in the muscle fibers.
- Deltoid impingement: Compression of the deltoid muscle between the acromion process and the humerus.
- Axillary nerve palsy: Damage to the nerve that innervates the deltoid muscle.
Treatment for deltoid muscle injuries depends on the severity of the injury. Conservative treatment may include rest, ice, compression, and elevation (RICE), as well as physical therapy. Surgical treatment may be necessary for severe injuries.
Conclusion
The deltoid muscle is a complex and important shoulder muscle. Understanding its anatomy and function is essential for proper diagnosis and treatment of shoulder injuries.
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